list1=['1','2','3','4']
list2=list(map(int,list1))
print(list2)

def change(x):
    return x+"--"
ls=list(map(change,list1))
print(ls)

ls1=list(map(lambda x:x+"--",list1))
print(ls)

list3=[1,-1,0,2,-2,-3]
a=lambda x:-x if x<0 else x
ls2=list(map(lambda x:-x if x<0 else x,list3))
print(ls2)